(a) Field of the Invention
The present invention relates a method for supporting session mobility. More particularly, the present invention relates to a method for supporting session mobility that is capable of moving various sessions using session initiation protocol (SIP).
(b) Description of the Related Art
Recently, the Internet network has been used for various services such as a communication service, a streaming service, as well as an information exchange service.
For those services, at least one session is created between a service provider (hereinafter called a server) and a service receiver (hereinafter called a client). The session generally includes a session ID and session information, that is, data corresponding to the session ID. The session ID is stored at the client and the session information is stored at the server. When the client is disconnected from the server, it is impossible to re-connect to the server without the session information.
For example, when a client establishes a session with a server using a mobile terminal, if he changes to use a fixed terminal in order to save a high cost, then the session is not well preserved using the fixed terminal. So the client manually establish a new session with the server to use the service continuously.
Recently various methods for supporting session mobility have been proposed.
FIG. 1 is a flowchart for supporting session mobility using SIP REFER method.
A first terminal unit 10 sends a SIP INVITE message to a second terminal unit 11 to request SIP session establishment (S10), the second terminal unit 11 sends a 200 OK message to respond to the session establishment request (S11), and the first terminal unit 10 sends a SIP ACK message acknowledging to the 200 OK message to establish a SIP session (S12).
Then, the second terminal unit 11 moves the SIP session with the first terminal unit 10 to a third terminal 12 as follows. The second terminal unit 11 sends a SIP REFER message to the third terminal unit 12 which cause the third terminal unit 12 to request SIP session establishment with the first terminal unit 10 using the session information from the SIP REFER message (S13).
The third terminal unit 12 sends a SIP NOTIFY message to the second terminal unit 11 to notify of accepting the session transfer request (S14).
The third terminal unit 12 sends a SIP INVITE message to the first terminal unit 10 to request session establishment. The SIP INVITE message includes information for requesting the first terminal unit 10 to close the session with the second terminal unit 11 (S15).
The first terminal unit 10 sends a 200 OK message to respond the session establishment request (S16), and the third terminal unit 12 sends the SIP ACK message acknowledging to the 200 OK messages to establish a SIP session (S17).
The first terminal unit 10 terminates the session established between the first terminal unit 10 and the second terminal unit 11 according to an information in the SIP INVITE message received from the third terminal unit 12.
A method for supporting session mobility disclosed in US Patent Application Publication U.S. 2003/0195963 A1 is described with reference to FIG. 2.
When a user accesses a web server 22 using a web browser at the first terminal unit 20, a session is established between the user and the web server (S20). Then, the user generates a snapshot of the session and transfers the snapshot to a browser session preservation and movement (BSPM) proxy server 21 (S21). When the user accesses the BSPM proxy server using a web browser at a second terminal unit 23, the user receives the snapshot of the session generated before (S22). Next, the second terminal unit 23 accesses the web server 22, and establishes and preserves the session using session information in the snapshot (S23).
However, the SIP REFER method for supporting session mobility according to a previous work shown in FIG. 1 includes only information of the other party of the session. So the characteristic of the session cannot be preserved. Also, the SIP REFER method only supports mobility of SIP INVITE-initiated session. The BSPM proxy approach for supporting session mobility according to the previous work shown in FIG. 2 only supports mobility of the web session.
Moreover above-mentioned approaches for supporting session mobility can be applied to support mobility of one session. So, when many sessions are need to be moved from one terminal to another terminal, there is a problem in that those sessions should be moved one by one.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person or ordinary skill in the art.